Removed global (p) navigation.

If you want to manage score setup you should use (p) at the ScorePackageManager
main menu.

Previously you could use (p) anywhere inside a score. This commit removes that
extra navigation affordance.

This means that these six global navigation commands ...

    build (u)
    distribution (d)
    makers (k)
    materials (m)
    segments (g)
    stylesheets (y)

... now work inside scores and outside of scores equally.

So use (y) anytime anywhere. But use (p) only at ScorePackageManager main menu.